Native wildflower establishment with imidazolinone herbicides

Native wildflowers are important components of grassland communities and lo w-maintenance wildflower seed mixtures. Weed interference limits successful establishment of native wildflowers from seed. Experiments were conducted to determine the influence of the imidazolinone herbicides imazethapyr, ima zapic, and imazaquin on the establishment of blackeyed susan (Rudbeckia hir ta L.), upright prairieconeflower [Ratibida columnifera (Nutt) Woot. and St andl.], spiked liatris [Liatris spicata (L.) Willd,], blanket flower (Gaill ardia aristata Pursh,), purple coneflower [Echinacea purpurea (L.) Moench.] , and spotted beebalm (Monarda punctata L,), Wildflower response to the her bicide treatments was variable and appeared to be influenced by the level o f weed interference. Establishment of the native wildflowers after applicat ion of imazethapyr or imazapic at 70 g . ha(-1) a.i. was generally improved at sites with greater weed interference. Emergence and density of wildflow ers was often reduced by imazapic in sites with low weed interference. Flow er density during the second growing season was usually either improved or not reduced by either imazethapyr or imazapic, Based on these findings, ima zethapyr and imazapic can reduce weed interference and improve the establis hment of some native wildflowers in areas with high weed infestations. Chem ical names used: (+/-) -2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H- imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid (imazapic); 2-[4,5-dihydr o-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid (imazaquin); 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidaz ol-2-yl]-5-ethyl-3-pyridinecarboxylic acid (imazethapyr).